Patent Grant
8147019
This application is based on Japanese Patent Application Nos. 11-236260 filed on Aug. 24, 1999 and 2000-219758 filed Jul. 19, 2000, the content of which is incorporated hereinto by reference.
1. Field of the Invention
The present invention relates to a print position adjustment method and a printing apparatus and a printing system using the print position adjustment method, and is particularly suited for adjusting the positions of ink dots in a printing apparatus of an ink jet system. In addition to general printing apparatus, the present invention can also be applied to copying machines, facsimiles with a communication system, word processors with a printer, and industrial printing apparatus combined with a variety of processing devices.
2. Description of the Related Art
An image printing apparatus of a so-called serial scan type, which executes the print operation while scanning a print head, or a printing unit, over a print medium, has found a variety of image forming applications. The ink jet printing apparatus in particular has in recent years achieved high resolution and color printing, making a significant image quality improvement, which has resulted in a rapid spread of its use. Such an apparatus employs a so-called multi-nozzle head that has an array of densely arranged nozzles for ejecting ink droplets. Images with still higher resolution have now been made possible by increasing the nozzle density and reducing the amount of ink per dot. Further, to realize an image quality approaching that of a silver salt picture, various technologies have been developed, including the use of pale or light color ink with reduced concentration in addition to four basic color inks (cyan, magenta, yellow and black). A print speed reduction problem, which is feared to arise as the picture quality advances, is dealt with by increasing the number of print elements, improving the drive frequency and employing a bi-directional printing technique, thus realizing a satisfactory throughput.
Designated 1903 is a paper feed roller which, in cooperation with an auxiliary roller 1904, clamps a print medium (print paper) 1907 and rotates in the direction of arrow in the figure to feed the print paper 1907 in the Y direction as required. Denoted 1905 is a pair of paper supply rollers that clamps the print paper 1907 and carries it toward the print position. The paper supply rollers 1905 also keep the print paper 1907 flat and tight between the supply rollers and the feed rollers 1903, 1904.
Designated 1906 is a carriage that supports the four head cartridges 1901 and moves them in a main scan direction during the print operation. When the printing is not performed or during an ink ejection performance recovery operation for the head unit 1902H, the carriage 1906 is set at a home position h indicated by a dotted line.
The carriage 1906, which was set at the home position h before the print operation, starts moving in the X direction upon reception of a print start command and at the same time the head unit 1902H ejects ink from a plurality of nozzles (n nozzles) formed therein according to print data to perform printing over a band of a width corresponding to the length of the nozzle array. When the printing is done up to the X-direction end of the print paper 1907, the carriage 1906 returns to the home position h in the case of one-way printing and resumes printing in the X direction. In the case of bi-directional printing, the carriage 1906 also performs printing while it is moving in a −X direction toward the home position h. In either case, after one print operation (one scan) in one direction has been finished before the next print operation is started, the paper feed roller 1903 is rotated a predetermined amount in the direction of arrow in the figure to feed the print paper 1907 in the Y direction a predetermined distance (corresponding to the length of the nozzle array). By repeating the one-scan print operation and the print paper feeding by a predetermined distance, data for one sheet of paper is printed.
In the above serial type ink jet printer, various provisions have been made as to the construction of the head unit or the printing method in order to realize an image printing with higher resolution.
For example, the manufacture of the multi-nozzle head inevitably places a limit on the density of the nozzles in a single nozzle array.
In other technologies, such as U.S. Pat. No. 4,920,355 and Japanese Patent Application Laid-Open No. 7-242025 (1995), a high resolution printing is realized by setting the paper feed distance for each print scan to a predetermined number of pixels less than the length of the column of nozzles while leaving the multi-nozzle arrangement at a low resolution. Such a printing method is hereinafter called an interlace printing method.
The interlace printing method will be briefly explained by referring to
While in this example the paper is fed a fixed distance of 9 pixels at 1200-DPI resolution, other arrangements may be made in the interlace printing. The interlace printing method does not need to have a constant paper feed distance at all times as long as a picture is printed with a plurality of print scans arranged at a pitch finer than the arrangement pitch of the nozzles themselves. In either case, an image can be printed with a higher resolution than the nozzle arrangement resolution.
When a head as shown in
Many proposals have been put forward as to the method of correcting ink landing position deviations among different colors and, in the bi-directional printing, the method of correcting deviations in ink landing position of the same color between the forward scan and the backward scan. However, as for the correction of the ink landing position deviations between the rasters of the same color produced by the head shown in
Further, in the interlace printing method, because the same image area is completed by repeating the print scan and the paper feed a plurality of times, the printing time will increase. To cope with this problem, a bi-directional printing has been proposed and disclosed. In this case, the odd-numbered rasters are often printed by the forward scans and the even-numbered rasters by backward scans, as shown in
There are many proposals already put forth as to the method of correcting ink landing position deviations between forward scan and backward scan. The proposed methods mostly take note of a vertical line pattern where the same image area is completed by a single scan (one pass printing), and do not address the problem of correcting subtle deviations among the rasters when performing the interlace printing.
The present invention has been accomplished under these circumstances and its object is to make it possible to prevent an image quality degradation due to subtle ink dot forming position deviations among the rasters and thereby form high quality images at all times.
Further, in the bi-directional printing, in particular, the higher the resolution of the image, the more stringent the required dot landing position accuracy becomes, so that a dot landing position deviation of even several μm will result in a perceivable degradation of image quality and, therefore, another object of the present invention is to make it possible to set the dot position adjustment value properly and in real time according to characteristic variations, within tolerance, of the print head and the printer body as well as according to the state of the printing operation.
In a first aspect of the present invention, there is provided a print position adjusting method for a printing apparatus, wherein the printing apparatus uses a print head having an array of a plurality of print elements and forms an image on a print medium by scanning the print head in a direction different from an arranging direction of the plurality of print elements and wherein rasters making up the image are divided into at least two raster groups according to a driving mode of the plurality of print elements, the method for adjusting print positions by the plurality of print elements between the at least two raster groups, the method comprising the steps of:
forming a plurality of adjustment patterns by the print head, in a manner that a print element drive timing between the at least two raster groups is shifted a predetermined interval, the print element drive timing being a timing of driving the plurality of print elements;
entering an adjustment value for the print element drive timing between the at least two raster groups, the adjustment value being determined from the plurality of adjustment patterns; and
storing the entered adjustment value.
In a second aspect of the present invention, there is provided a print position adjusting method for a printing apparatus, wherein the printing apparatus uses a print head having an array of a plurality of nozzles for ejecting ink and forms an image on a print medium by scanning the print head in forward and backward directions different from an arranging direction of the plurality of nozzles and wherein a speed of the scan and a distance from the nozzles to the print medium can be set in at least two stages respectively, the method for adjusting positions of ink dots ejected from the plurality of nozzles between the scans in the forward and backward directions, the method comprising the steps of:
forming a plurality of adjustment patterns by the print head, in a manner that an ink ejection timing between the forward and backward scans is shifted by a predetermined interval, the ink ejection timing being a timing of ejecting ink from the plurality of nozzles;
entering an adjustment value for the ink ejection timing between the forward and backward scans, the adjustment value being determined from the plurality of adjustment patterns;
storing the entered adjustment value; and
correcting the adjustment value according to a combination of the scan speed and the distance in performing a print operation.
In a third aspect of the present invention, there is provided a printing apparatus using a print head having an array of a plurality of print elements and forming an image on a print medium by scanning the print head in a direction different from an arranging direction of the plurality of print elements, wherein rasters making up the image are divided into at least two raster groups according to a driving mode of the plurality of print elements, the apparatus comprising:
means for forming a plurality of adjustment patterns by the print head, in a manner that a print element drive timing between the at least two raster groups is shifted a predetermined interval, the print element drive timing being a timing of driving the plurality of print elements; and
means for storing an adjustment value for the print element drive timing between the at least two raster groups, the adjustment value being supplied based on judgement of the plurality of adjustment patterns.
In a fourth aspect of the present invention, there is provided a printing apparatus using a print head having an array of a plurality of nozzles for ejecting ink and forming an image on a print medium by scanning the print head in forward and backward directions different from an arranging direction of the plurality of nozzles, wherein a speed of the scan and a distance from the nozzles to the print medium can be set in at least two stages respectively, the apparatus comprising:
means for forming a plurality of adjustment patterns by the print head, in a manner that an ink ejection timing between the forward and backward scans is shifted by a predetermined interval, the ink ejection timing being a timing of ejecting ink from the plurality of nozzles;
means for storing an adjustment value for the ink ejection timing between the forward and backward scans, the adjustment value being supplied based on judgement of the plurality of adjustment patterns; and
means for correcting the adjustment value according to a combination of the scan speed and the distance in performing a print operation.
In a fifth aspect of the present invention, there is provided a printing system comprising:
a printing apparatus using a print head having an array of a plurality of print elements and forming an image on a print medium by scanning the print head in a direction different from an arranging direction of the plurality of print elements, wherein rasters making up the image are divided into at least two raster groups according to a driving mode of the plurality of print elements, the apparatus having:
means for forming a plurality of adjustment patterns by the print head, in a manner that a print element drive timing between the at least two raster groups is shifted a predetermined interval, the print element drive timing being a timing of driving the plurality of print elements; and
means for storing an adjustment value for the print element drive timing between the at least two raster groups, the adjustment value being supplied based on judgement of the plurality of adjustment patterns; and
a host apparatus for supplying image data to the printing apparatus, having:
means for controlling the printing apparatus to form the plurality of adjustment patterns;
means for accepting entering of the adjustment value based on judgement of the plurality of adjustment patterns; and
means for supplying the adjustment data to the printing apparatus.
In a sixth aspect of the present invention, there is provided a printing system comprising:
a printing apparatus using a print head having an array of a plurality of nozzles for ejecting ink and forming an image on a print medium by scanning the print head in forward and backward directions different from an arranging direction of the plurality of nozzles, wherein a speed of the scan and a distance from the nozzles to the print medium can be set in at least two stages respectively, the apparatus having:
means for forming a plurality of adjustment patterns by the print head, in a manner that an ink ejection timing between the forward and backward scans is shifted by a predetermined interval, the ink ejection timing being a timing of ejecting ink from the plurality of nozzles;
means for storing an adjustment value for the ink ejection timing between the forward and backward scans, the adjustment value being supplied based on judgement of the plurality of adjustment patterns; and
means for correcting the adjustment value according to a combination of the scan speed and the distance in performing a print operation; and
a host apparatus for supplying image data to the printing apparatus, having:
means for controlling the printing apparatus to form the plurality of adjustment patterns;
means for accepting entering of the adjustment value based on judgement of the plurality of adjustment patterns; and
means for supplying the adjustment data to the printing apparatus.
In a seventh aspect of the present invention, there is provided a storage medium storing a program for performing a print position adjusting method for a printing apparatus, wherein the printing apparatus uses a print head having an array of a plurality of print elements and forms an image on a print medium by scanning the print head in a direction different from an arranging direction of the plurality of print elements and wherein rasters making up the image are divided into at least two raster groups according to a driving mode of the plurality of print elements, the method for adjusting print positions by the plurality of print elements between the at least two raster groups, the method comprising the steps of:
forming a plurality of adjustment patterns by the print head, in a manner that a print element drive timing between the at least two raster groups is shifted a predetermined interval, the print element drive timing being a timing of driving the plurality of print elements;
entering an adjustment value for the print element drive timing between the at least two raster groups, the adjustment value being determined from the plurality of adjustment patterns; and
storing the entered adjustment value.
In an eighth aspect of the present invention, there is provided a storage medium storing a program for performing a print position adjusting method for a printing apparatus, wherein the printing apparatus uses a print head having an array of a plurality of nozzles for ejecting ink and forms an image on a print medium by scanning the print head in forward and backward directions different from an arranging direction of the plurality of nozzles and wherein a speed of the scan and a distance from the nozzles to the print medium can be set in at least two stages respectively, the method for adjusting positions of ink dots ejected from the plurality of nozzles between the scans in the forward and backward directions, the method comprising the steps of:
forming a plurality of adjustment patterns by the print head, in a manner that an ink ejection timing between the forward and backward scans is shifted by a predetermined interval, the ink ejection timing being a timing of ejecting ink from the plurality of nozzles;
entering an adjustment value for the ink ejection timing between the forward and backward scans, the adjustment value being determined from the plurality of adjustment patterns;
storing the entered adjustment value; and
correcting the adjustment value according to a combination of the scan speed and the distance in performing a print operation.
In a ninth aspect of the present invention, there is provided a print position adjusting method for adjusting a print position on a print medium during a forward scan and a print position on the print medium during a backward scan in a printing apparatus, wherein the printing apparatus removably supports a print head on which a plurality of ink ejection openings are arranged, and reciprocally scans the print head in a direction different from the arranging direction while ejecting ink to form an image, the method comprising the steps of:
referring first memory means in the printing apparatus storing first print position information associated with characteristic variations of the printing apparatus and second memory means in the print head storing second print position information associated with characteristic variations of the print head, before forming an image by mounting the print head on the printing apparatus; and
determining an adjustment value for adjusting the print position, based on the first and second print position information obtained by the referring.
In a tenth aspect of the present invention, there is provided a print position adjusting method for adjusting a print position on a print medium during a forward scan and a print position on the print medium during a backward scan in a printing apparatus, wherein the printing apparatus removably supports a print head on which a plurality of ink ejection openings are arranged, and reciprocally scans the print head in a direction different from the arranging direction while ejecting ink to form an image, the method comprising the steps of:
detecting a temperature of the print head;
estimating an ejection speed of ink ejected from said print head based on the detected temperature; and
determining an adjustment value for adjusting the print positions based on the estimated ejection speed.
In an eleventh aspect of the present invention, there is provided a print position adjusting method for adjusting a print position on a print medium during a forward scan and a print position on the print medium during a backward scan in a printing apparatus, wherein the printing apparatus removably supports a print head on which a plurality of ink ejection openings are arranged, and reciprocally scans the print head in a direction different from the arranging direction while ejecting ink to form an image, the method comprising the steps of:
detecting a temperature of the print head;
switching a drive frequency and a scan speed of the print head based on the detected temperature;
estimating an ejection speed of ink ejected from the print head based on the detected temperature; and
determining an adjustment value for adjusting the print positions based on the estimated ejection speed and the scan speed.
In a twelfth aspect of the present invention, there is provided a printing apparatus removably supporting a print head on which a plurality of ink ejection openings are arranged, and reciprocally scanning the print head in a direction different from the arranging direction while ejecting ink to form an image, the apparatus comprising:
first memory means for storing first print position information associated with characteristic variations of the printing apparatus;
means for referring the first memory means and second memory means in the print head storing second print position information associated with characteristic variations of the print head, before forming an image by mounting the print head on the printing apparatus; and
means for determining an adjustment value for adjusting a print position on a print medium during a forward scan and a print position on the print medium during a backward scan, based on the first and second print position information obtained by the referring.
In a thirteenth aspect of the present invention, there is provided a printing apparatus removably supporting a print head on which a plurality of ink ejection openings are arranged, and reciprocally scanning the print head in a direction different from the arranging direction while ejecting ink to form an image, the apparatus comprising:
means for detecting a temperature of the print head;
means for estimating an ejection speed of ink ejected from said print head based on the detected temperature; and
means for determining an adjustment value for adjusting a print position on a print medium during a forward scan and a print position on the print medium during a backward scan based on the estimated ejection speed.
In a fourteenth aspect of the present invention, there is provided a printing apparatus removably supporting a print head on which a plurality of ink ejection openings are arranged, and reciprocally scanning the print head in a direction different from the arranging direction while ejecting ink to form an image, the apparatus comprising:
means for detecting a temperature of the print head;
means for switching a drive frequency and a scan speed of the print head based on the detected temperature;
means for estimating an ejection speed of ink ejected from the print head based on the detected temperature; and
determining an adjustment value for adjusting a print position on a print medium during a forward scan and a print position on the print medium during a backward scan based on the estimated ejection speed and the scan speed.
The above and other objects, effects, features and advantages of the present invention will become more apparent from the following description of embodiments thereof taken in conjunction with the accompanying drawings.
Embodiments of the printing apparatus according to the present invention will be described by referring to the accompanying drawings.
In the following description we take up as an example a printing apparatus using an ink jet printing system.
In this specification, a word “print” (or “record”) refers to not only forming significant information, such as characters and figures, but also forming images, designs or patterns on printing medium and processing media, whether the information is significant or insignificant or whether it is visible so as to be perceived by humans.
The word “print medium” or “print sheet” includes not only paper used in common printing apparatus, but cloth, plastic films, metal plates, glass, ceramics, wood, leather or any other material that can receive ink. This word will be also referred to as “paper”.
Further, the word “ink” (or “liquid”) should be interpreted in its wide sense as with the word “print” and refers to liquid that is applied to the printing medium to form images, designs or patterns, process the printing medium or process ink (for example, coagulate or make insoluble a colorant in the ink applied to the printing medium).
The chassis M3019 is made of a plurality of plate-like metal members with a predetermined rigidity to form a skeleton of the printing apparatus and holds various printing operation mechanisms described later.
The lower case M1001 forms roughly a lower half of the housing of the printer body M1000 and the upper case M1002 forms roughly an upper half of the printer body M1000. These upper and lower cases, when combined, form a hollow structure having an accommodation space therein to accommodate various mechanisms described later. The printer body M1000 has an opening in its top portion and front portion.
The discharge tray M1004 has one end portion thereof rotatably supported on the lower case M1001. The discharge tray M1004, when rotated, opens or closes an opening formed in the front portion of the lower case M1001. When the print operation is to be performed, the discharge tray M1004 is rotated forwardly to open the opening so that printed sheets can be discharged and successively stacked. The discharge tray M1004 accommodates two auxiliary trays M1004a, M1004b. These auxiliary trays can be drawn out forwardly as required to expand or reduce the paper support area in three steps.
The access cover M1003 has one end portion thereof rotatably supported on the upper case M1002 and opens or closes an opening formed in the upper surface of the upper case M1002. By opening the access cover M1003, a print head cartridge H1000 or an ink tank H1900 installed in the body can be replaced. When the access cover M1003 is opened or closed, a projection formed at the back of the access cover, not shown here, pivots a cover open/close lever. Detecting the pivotal position of the lever as by a micro-switch and so on can determine whether the access cover is open or closed.
At the upper rear surface of the upper case M1002 a power key E0018, a resume key E0019 and an LED E0020 are provided. When the power key E0018 is pressed, the LED E0020 lights up indicating to an operator that the apparatus is ready to print. The LED E0020 has a variety of display functions, such as alerting the operator to printer troubles as by changing its blinking intervals and color. Further, a buzzer E0021 (
Next, a printing operation mechanism installed and held in the printer body M1000 according to this embodiment will be explained.
The printing operation mechanism in this embodiment comprises: an automatic sheet feed unit M3022 to automatically feed a print sheet into the printer body; a sheet transport unit M3029 to guide the print sheets, fed one at a time from the automatic sheet feed unit, to a predetermined print position and to guide the print sheet from the print position to a discharge unit M3030; a print unit to perform a desired printing on the print sheet carried to the print position; and an ejection performance recovery unit M5000 to recover the ink ejection performance of the print unit.
Here, the print unit will be described. The print unit comprises a carriage M4001 movably supported on a carriage shaft M4021 and a print head cartridge H1000 removably mounted on the carriage M4001.
First, the print head cartridge used in the print unit will be described with reference to
The print head cartridge H1000 in this embodiment, as shown in
The ink tank for this print head cartridge H1000 consists of separate ink tanks H1900 of, for example, black, light cyan, light magenta, cyan, magenta and yellow to enable color printing with as high an image quality as a photograph. As shown in
Then, the print head H1001, as shown in the perspective view of
The print element silicon substrate H1100 has formed in one of its surfaces, by the film deposition technology, a plurality of print elements to produce energy for ejecting ink and electric wires, such as aluminum, for supplying electricity to individual print elements. A plurality of ink passages and a plurality of nozzles H1100T, both corresponding to the print elements, are also formed by the photolithography technology. In the back of the print element substrate H1100, there are formed ink supply ports for supplying ink to the plurality of ink passages. The print element substrate H1100 is securely bonded to the first plate H1200 which is formed with ink supply ports H1201 for supplying ink to the print element substrate H1100. The first plate H1200 is securely bonded with the second plate H1400 having an opening. The second plate H1400 holds the electric wiring board H1300 to electrically connect the electric wiring board H1300 with the print element substrate H1100. The electric wiring board H1300 is to apply electric signals for ejecting ink to the print element substrate H1100, and has electric wires associated with the print element substrate HI100 and external signal input terminals H1301 situated at electric wires' ends for receiving electric signals from the printer body. The external signal input terminals H1301 are positioned and fixed at the back of a tank holder H1500 described later.
The tank holder H1500 that removably holds the ink tank H1900 is securely attached, as by ultrasonic fusing, with the flow passage forming member H1600 to form an ink passage H1501 from the ink tank H1900 to the first plate H1200. At the ink tank side end of the ink passage H1501 that engages with the ink tank H1900, a filter H1700 is provided to prevent external dust from entering. A seal rubber H1800 is provided at a portion where the filter H1700 engages the ink tank H1900, to prevent evaporation of the ink from the engagement portion.
As described above, the tank holder unit, which includes the tank holder H1500, the flow passage forming member H1600, the filter H1700 and the seal rubber H1800, and the print element unit, which includes the print element substrate H1100, the first plate H1200, the electric wiring board H1300 and the second plate H1400, are combined as by adhesives to form the print head H1001.
Next, by referring to
As shown in
That is, the head set lever M4007 is provided at the upper part of the carriage M4001 so as to be pivotable about a head set lever shaft. There is a spring-loaded head set plate (not shown) at an engagement portion where the carriage M4001 engages the print head H1001. With the spring force, the head set lever M4007 presses against the print head H1001 to mount it on the carriage M4001.
At another engagement portion of the carriage M4001 with the print head H1001, there is provided a contact flexible printed cable (see
Between the contract portion of the contact FPC E0011 and the carriage M4001 there is an elastic member not shown, such as rubber. The elastic force of the elastic member and the pressing force of the head set lever spring combine to ensure a reliable contact between the contact portion of the contact FPC E0011 and the carriage M4001. Further, the contact FPC E0011 is connected to a carriage substrate E0013 mounted at the back of the carriage M4001 (see
The printer of this embodiment can mount a scanner in the carriage M4001 in place of the print head cartridge H1000 and be used as a reading device.
The scanner moves together with the carriage M4001 in the main scan direction, and reads an image on a document fed instead of the printing medium as the scanner moves in the main scan direction. Alternating the scanner reading operation in the main scan direction and the document feed in the sub-scan direction enables one page of document image information to be read.
As shown in the figure, a scanner holder M6001 is shaped like a box and contains an optical system and a processing circuit necessary for reading. A reading lens M6006 is provided at a portion that faces the surface of a document when the scanner M6000 is mounted on the carriage M4001. The lens M6006 focuses light reflected from the document surface onto a reading unit inside the scanner to read the document image. An illumination lens M6005 has a light source not shown inside the scanner. The light emitted from the light source is radiated onto the document through the lens M6005.
The scanner cover M6003 secured to the bottom of the scanner holder M6001 shields the interior of the scanner holder M6001 from light. Louver-like grip portions are provided at the sides to improve the ease with which the scanner can be mounted to and dismounted from the carriage M4001. The external shape of the scanner holder M6001 is almost similar to that of the print head H1001, and the scanner can be mounted to or dismounted from the carriage M4001 in a manner similar to that of the print head H1001.
The scanner holder M6001 accommodates a substrate having a reading circuit, and a scanner contact PCB M6004 connected to this substrate is exposed outside. When the scanner M6000 is mounted on the carriage M4001, the scanner contact PCB M6004 contacts the contact FPC E0011 of the carriage M4001 to electrically connect the substrate to a control system on the printer body side through the carriage M4001.
Next, an electric circuit configuration in this embodiment of the invention will be explained.
The electric circuit in this embodiment comprises mainly a carriage substrate (CRPCB) E0013, a main PCB (printed circuit board) E0014 and a power supply unit E0015.
The power supply unit E0015 is connected to the main PCB E0014 to supply a variety of drive power.
The carriage substrate E0013 is a printed circuit board unit mounted on the carriage M4001 (
Further, the main PCB E0014 is a printed circuit board unit that controls the operation of various parts of the ink jet printing apparatus in this embodiment, and has I/O ports for a paper end sensor (PE sensor) E0007, an automatic sheet feeder (ASF) sensor E0009, a cover sensor E0022, a parallel interface (parallel I/F) E0016, a serial interface (Serial I/F) E0017, a resume key E0019, an LED E0020, a power key E0018 and a buzzer E0021. The main PCB E0014 is connected to and controls a motor (CR motor) E0001 that constitutes a drive source for moving the carriage M4001 in the main scan direction; a motor (LF motor) E0002 that constitutes a drive source for transporting the printing medium; and a motor (PG motor) E0003 that performs the functions of recovering the ejection performance of the print head and feeding the printing medium. The main PCB E0014 also has connection interfaces with an ink empty sensor E0006, a gap sensor E0008, a PG sensor E0010, the CRFFC E0012 and the power supply unit E0015.
Reference number E1001 represents a CPU, which has a clock generator (CG) E1002 connected to an oscillation circuit E1005 to generate a system clock based on an output signal E1019 of the oscillation circuit E1005. The CPU E1001 is connected to an ASIC (application specific integrated circuit) and a ROM E1004 through a control bus E1014. According to a program stored in the ROM E1004, the CPU E1001 controls the ASIC E1006, checks the status of an input signal E1017 from the power key, an input signal E1016 from the resume key, a cover detection signal E1042 and a head detection signal (HSENS) E1013, drives the buzzer E0021 according to a buzzer signal (BUZ) E1018, and checks the status of an ink empty detection signal (INKS) E1011 connected to a built-in A/D converter E1003 and of a temperature detection signal (TH) E1012 from a thermistor. The CPU E1001 also performs various other logic operations and makes conditional decisions to control the operation of the ink jet printing apparatus.
The head detection signal E1013 is a head mount detection signal entered from the print head cartridge H1000 through the flexible flat cable E0012, the carriage substrate E0013 and the contact FPC E0011. The ink empty detection signal E1011 is an analog signal output from the ink empty sensor E0006. The temperature detection signal E1012 is an analog signal from the thermistor (not shown) provided on the carriage substrate E0013.
Designated E1008 is a CR motor driver that uses a motor power supply (VM) E1040 to generate a CR motor drive signal E1037 according to a CR motor control signal E1036 from the ASIC E1006 to drive the CR motor E0001. E1009 designates an LF/PG motor driver which uses the motor power supply E1040 to generate an LF motor drive signal E1035 according to a pulse motor control signal (PM control signal) E1033 from the ASIC E1006 to drive the LF motor. The LF/PG motor driver E1009 also generates a PG motor drive signal E1034 to drive the PG motor.
Designated E1010 is a power supply control circuit which controls the supply of electricity to respective sensors with light emitting elements according to a power supply control signal E1024 from the ASIC E1006. The parallel I/F E0016 transfers a parallel I/F signal E1030 from the ASIC E1006 to a parallel I/F cable E1031 connected to external circuits and also transfers a signal of the parallel I/F cable E1031 to the ASIC E1006. The serial I/F E0017 transfers a serial I/F signal E1028 from the ASIC E1006 to a serial I/F cable E1029 connected to external circuits, and also transfers a signal from the serial I/F cable E1029 to the ASIC E1006.
The power supply unit E0015 provides a head power signal (VH) E1039, a motor power signal (VM) E1040 and a logic power signal (VDD) E1041. A head power ON signal (VHON) E1022 and a motor power ON signal (VMON) E1023 are sent from the ASIC E1006 to the power supply unit E0015 to perform the ON/OFF control of the head power signal E1039 and the motor power signal E1040. The logic power signal (VDD) E1041 supplied from the power supply unit E0015 is voltage-converted as required and given to various parts inside or outside the main PCB E0014.
The head power signal E1039 is smoothed by a circuit of the main PCB E0014 and then sent out to the flexible flat cable E0011 to be used for driving the print head cartridge H1000. E1007 denotes a reset circuit which detects a reduction in the logic power signal E1041 and sends a reset signal (RESET) to the CPU E1001 and the ASIC E1006 to initialize them.
The ASIC E1006 is a single-chip semiconductor integrated circuit and is controlled by the CPU E1001 through the control bus E1014 to output the CR motor control signal E1036, the PM control signal E1033, the power supply control signal E1024, the head power ON signal E1022 and the motor power ON signal E1023. It also transfers signals to and from the parallel interface E0016 and the serial interface E0017. In addition, the ASIC E1006 detects the status of a PE detection signal (PES) E1025 from the PE sensor E0007, an ASF detection signal (ASFS) E1026 from the ASF sensor E0009, a gap detection signal (GAPS) E1027 from the GAP sensor E0008 for detecting a gap between the print head and the printing medium, and a PG detection signal (PGS) E1032 from the PG sensor E0010, and sends data representing the statuses of these signals to the CPU E1001 through the control bus E1014. Based on the data received, the CPU E1001 controls the operation of an LED drive signal E1038 to turn on or off the LED E0020.
Further, the ASIC E1006 checks the status of an encoder signal (ENC) E1020, generates a timing signal, interfaces with the print head cartridge H1000 and controls the print operation by a head control signal E1021. The encoder signal (ENC) E1020 is an output signal of the CR encoder sensor E0004 received through the flexible flat cable E0012. The head control signal E1021 is sent to the print head H1001 through the flexible flat cable E0012, carriage substrate E0013 and contact FPC E0011.
In these figures, only the flow of data, such as print data and motor control data, associated with the control of the head and various mechanical components is shown between each block, and control signals and clock associated with the read/write operation of the registers incorporated in each block and control signals associated with the DMA control are omitted to simplify the drawing.
In the figures, reference number E2002 represents a PLL controller which, based on a clock signal (CLK) E2031 and a PLL control signal (PLLON) E2033 output from the CPU E1001, generates a clock (not shown) to be supplied to most of the components of the ASIC E1006.
Denoted E2001 is a CPU interface (CPU I/F) E2001, which controls the read/write operation of register in each block, supplies a clock to some blocks and accepts an interrupt signal (none of these operations are shown) according to a reset signal E1015, a software reset signal (PDWN) E2032 and a clock signal (CLK) E2031 output from the CPU E1001, and control signals from the control bus E1014. The CPU I/F E2001 then outputs an interrupt signal (INT) E2034 to the CPU E1001 to inform it of the occurrence of an interrupt within the ASIC E1006.
E2005 denotes a DRAM which has various areas for storing print data, such as a reception buffer E2010, a work buffer E2011, a print buffer E2014 and a development data buffer E2016. The DRAM E2005 also has a motor control buffer E2023 for motor control and, as buffers used instead of the above print data buffers during the scanner operation mode, a scanner input buffer E2024, a scanner data buffer E2026 and an output buffer E2028.
The DRAM E2005 is also used as a work area by the CPU E1001 for its own operation. Designated E2004 is a DRAM control unit E2004 which performs read/write operations on the DRAM E2005 by switching between the DRAM access from the CPU E1001 through the control bus and the DRAM access from a DMA control unit E2003 described later.
The DMA control unit E2003 accepts request signals (not shown) from various blocks and outputs address signals and control signals (not shown) and, in the case of write operation, write data E2038, E2041, E2044, E2053, E2055, E2057 etc. to the DRAM control unit to make DRAM accesses. In the case of read operation, the DMA control unit E2003 transfers the read data E2040, E2043, E2045, E2051, E2054, E2056, E2058, E2059 from the DRAM control unit E2004 to the requesting blocks.
Denoted E2006 is an IEEE 1284 I/F which functions as a bi-directional communication interface with external host devices, not shown, through the parallel I/F E0016 and is controlled by the CPU E1001 via CPU I/F E2001. During the printing operation, the IEEE 1284 I/F E2006 transfers the receive data (PIF receive data E2036) from the parallel I/F E0016 to a reception control unit E2008 by the DMA processing. During the scanner reading operation, the 1284 I/F E2006 sends the data (1284 transmit data (RDPIF) E2059) stored in the output buffer E2028 in the DRAM E2005 to the parallel I/F E0016 by the DMA processing.
Designated E2007 is a universal serial bus (USB) I/F which offers a bi-directional communication interface with external host devices, not shown, through the serial I/F E0017 and is controlled by the CPU E1001 through the CPU I/F E2001. During the printing operation, the universal serial bus (USB) I/F E2007 transfers received data (USB receive data E2037) from the serial I/F E0017 to the reception control unit E2008 by the DMA processing. During the scanner reading, the universal serial bus (USB) I/F E2007 sends data (USB transmit data (RDUSB) E2058) stored in the output buffer E2028 in the DRAM E2005 to the serial OF E0017 by the DMA processing. The reception control unit E2008 writes data (WDIF E2038) received from the 1284 I/F E2006 or universal serial bus (USB) I/F E2007, whichever is selected, into a reception buffer write address managed by a reception buffer control unit E2039.
Designated E2009 is a compression/decompression DMA controller which is controlled by the CPU E1001 through the CPU I/F E2001 to read received data (raster data) stored in a reception buffer E2010 from a reception buffer read address managed by the reception buffer control unit E2039, compress or decompress the data (RDWK) E2040 according to a specified mode, and write the data as a print code string (WDWK) E2041 into the work buffer area.
Designated E2013 is a print buffer transfer DMA controller which is controlled by the CPU E1001 through the CPU IN E2001 to read print codes (RDWP) E2043 on the work buffer E2011 and rearrange the print codes onto addresses on the print buffer E2014 that match the sequence of data transfer to the print head cartridge H1000 before transferring the codes (WDWP E2044). Reference number E2012 denotes a work area DMA controller which is controlled by the CPU E1001 through the CPU I/F E2001 to repetitively write specified work fill data (WDWF) E2042 into the area of the work buffer whose data transfer by the print buffer transfer DMA controller E2013 has been completed.
Designated E2015 is a print data development DMA controller E2015, which is controlled by the CPU E1001 through the CPU I/F E2001. Triggered by a data development timing signal E2050 from a head control unit E2018, the print data development DMA controller E2015 reads the print code that was rearranged and written into the print buffer and the development data written into the development data buffer E2016 and writes developed print data (RDHDG) E2045 into the column buffer E2017 as column buffer write data (WDHDG) E2047. The column buffer E2017 is an SRAM that temporarily stores the transfer data (developed print data) to be sent to the print head cartridge H1000, and is shared and managed by both the print data development DMA CONTROLLER and the head control unit through a handshake signal (not shown).
Designated E2018 is a head control unit E2018 which is controlled by the CPU E1001 through the CPU I/F E2001 to interface with the print head cartridge H1000 or the scanner through the head control signal. It also outputs a data development timing signal E2050 to the print data development DMA controller according to a head drive timing signal E2049 from the encoder signal processing unit E2019.
During the printing operation, the head control unit E2018, when it receives the head drive timing signal E2049, reads developed print data (RDHD) E2048 from the column buffer and outputs the data to the print head cartridge H1000 as the head control signal E1021.
In the scanner reading mode, the head control unit E2018 DMA-transfers the input data (WDHD) E2053 received as the head control signal E1021 to the scanner input buffer E2024 on the DRAM E2005. Designated E2025 is a scanner data processing DMA controller E2025 which is controlled by the CPU E1001 through the CPU I/F E2001 to read input buffer read data (RDAV) E2054 stored in the scanner input buffer E2024 and writes the averaged data (WDAV) E2055 into the scanner data buffer E2026 on the DRAM E2005.
Designated E2027 is a scanner data compression DMA controller which is controlled by the CPU E1001 through the CPU I/F E2001 to read processed data (RDYC) E2056 on the scanner data buffer E2026, perform data compression, and write the compressed data (WDYC) E2057 into the output buffer E2028 for transfer.
Designated E2019 is an encoder signal processing unit which, when it receives an encoder signal (ENC), outputs the head drive timing signal E2049 according to a mode determined by the CPU E1001. The encoder signal processing unit E2019 also stores in a register information on the position and speed of the carriage M4001 obtained from the encoder signal E1020 and presents it to the CPU E1001. Based on this information, the CPU E1001 determines various parameters for the CR motor E0001. Designated E2020 is a CR motor control unit which is controlled by the CPU E1001 through the CPU I/F E2001 to output the CR motor control signal E1036.
Denoted E2022 is a sensor signal processing unit which receives detection signals E1032, E1025, E1026 and E1027 output from the PG sensor E0010, the PE sensor E0007, the ASF sensor E0009 and the gap sensor E0008, respectively, and transfers this sensor information to the CPU E1001 according to the mode determined by the CPU E1001. The sensor signal processing unit E2022 also outputs a sensor detection signal E2052 to a DMA controller E2021 for controlling the LF/PG motor.
The DMA controller E2021 for controlling LF/PG motor is controlled by the CPU E1001 through the CPU I/F E2001 to read a pulse motor drive table (RDPM) E2051 from the motor control buffer E2023 on the DRAM E2005 and output a pulse motor control signal E1033. Depending on the operation mode, the controller outputs the pulse motor control signal E1033 upon reception of the sensor detection signal as a control trigger.
Designated E2030 is an LED control unit which is controlled by the CPU E1001 through the CPU I/F E2001 to output an LED drive signal E1038. Further, designated E2029 is a port control unit which is controlled by the CPU E1001 through the CPU I/F E2001 to output the head power ON signal E1022, the motor power ON signal E1023 and the power supply control signal E1024.
Next, the operation of the ink jet printing apparatus in this embodiment of the invention with the above configuration will be explained by referring to the flow chart of
When the printer body M1000 is connected to an AC power supply, a first initialization is performed at step S1. In this initialization process, the electric circuit system including the ROM and RAM in the apparatus is checked to confirm that the apparatus is electrically operable.
Next, step S2 checks if the power key E0018 on the upper case M1002 of the printer body M1000 is turned on. When it is decided that the power key E0018 is pressed, the processing moves to the next step S3 where a second initialization is performed.
In this second initialization, a check is made of various drive mechanisms and the print head of this apparatus. That is, when various motors are initialized and head information is read, it is checked whether the apparatus is normally operable.
Next, step S4 waits for an event. That is, this step monitors a demand event from the external I/F, a panel key event from the user operation and an internal control event and, when any of these events occurs, executes the corresponding processing.
When, for example, step S4 receives a print command event from the external I/F, the processing moves to step S5. When a power key event from the user operation occurs at step S4, the processing moves to step S10. If another event occurs, the processing moves to step S11.
Step S5 analyzes the print command from the external I/F, checks a specified paper kind, paper size, print quality, paper feeding method and others, and stores data representing the check result into the DRAM E2005 of the apparatus before proceeding to step S6.
Next, step S6 starts feeding the paper according to the paper feeding method specified by the step S5 until the paper is situated at the print start position. The processing moves to step S7.
At step S7 the printing operation is performed. In this printing operation, the print data sent from the external I/F is stored temporarily in the print buffer. Then, the CR motor E0001 is started to move the carriage M4001 in the main-scanning direction. At the same time, the print data stored in the print buffer E2014 is transferred to the print head H1001 to print one line. When one line of the print data has been printed, the LF motor E0002 is driven to rotate the LF roller M3001 to transport the paper in the sub-scanning direction. After this, the above operation is executed repetitively until one page of the print data from the external IN is completely printed, at which time the processing moves to step S8.
At step S8, the LF motor E0002 is driven to rotate the paper discharge roller M2003 to feed the paper until it is decided that the paper is completely fed out of the apparatus, at which time the paper is completely discharged onto the paper discharge tray M1004.
Next at step S9, it is checked whether all the pages that need to be printed have been printed and if there are pages that remain to be printed, the processing returns to step S5 and the steps S5 to S9 are repeated. When all the pages that need to be printed have been printed, the print operation is ended and the processing moves to step S4 waiting for the next event.
Step S10 performs the printing termination processing to stop the operation of the apparatus. That is, to turn off various motors and print head, this step renders the apparatus ready to be cut off from power supply and then turns off power, before moving to step S4 waiting for the next event.
Step S11 performs other event processing. For example, this step performs processing corresponding to the ejection performance recovery command from various panel keys or external I/F and the ejection performance recovery event that occurs internally. After the recovery processing is finished, the printer operation moves to step S4 waiting for the next event.
The construction and arrangement of nozzles in the print head H1001 used in this embodiment will be described.
Various processing to achieve the object of the present invention by using the printing apparatus and head with the above construction will be explained in the following. The processing for obtaining a registration value described later can be defined as corresponding to the second initialization processing (step S3) in the procedure of
Because this embodiment is intended to enable the printing of mainly photographic images with high resolution, a multi-pass printing is normally performed. Here, the multi-pass printing will be briefly explained.
Unlike a monochromatic printing that prints only characters such as letters, numbers and symbols, the color image printing must meet various requirements such as color development, grayscale characteristic and uniformity. As to the uniformity in particular, slight variations among individual nozzles that are produced during the manufacture of a multi-nozzle head formed integrally with many nozzles (in this specification the nozzle generally refers to an ejection opening, a liquid passage communicating with the ejection opening and an element for generating energy used to eject ink) influence the amounts of ink ejected from the individual nozzles and the directions of ink ejection during printing and eventually degrade the image quality in the form of density variations of the printed image.
Detailed examples will be explained by referring to
In reality, however, individual nozzles have their own variations and if the printing is done in a manner described above, the ink droplets ejected from individual nozzles vary in size and direction as shown in
To deal with the problem of the unevenness in density, the following method has been proposed.
This method will be explained by referring to
While the same print area has been described to be completed in two scans, the multi-pass printing improves the image quality as the number of passes increases. This however elongates the print time, which means that there is a trade-off relation between the image quality and the print time. The printer of this embodiment, therefore, has provisions to enable not only a one-pass mode, which does not perform the multi-pass printing, but also multi-pass modes ranging from two passes to eight passes, allowing the user to select a desired print mode according to the kind of print medium and usage.
The head H1001 used in the printer of this embodiment has the construction explained in
A major point of the invention concerns the adjustment of dot formation positions, i.e., the adjustment of ink droplet landing positions (also referred to as print position adjustment or registration). The printer of this embodiment has a means to perform the landing position adjustment during the forward scan and the backward scan in the bi-directional printing (bi-directional registration) and a means to perform the landing position adjustment on even-numbered rasters formed by even-numbered columns of nozzles in
The EEPROM of the head H1001 may store various other information characteristic of the head H1001 in addition to the adjustment value for the O/E registration. Although the construction and effect of the EEPROM on the print head H1001 used in this embodiment conform basically to those of the technology disclosed in Japanese Patent Application Laid-Open No. 6-320732 (1994), the content of the stored data in the printing apparatus of this embodiment will be described in detail.
Further, as shown in
When the user obtains a print head H1001, mounts it on the carriage M4001 of the printer body and turns on power, the control unit of the printer body reads the content of the EEPROM of the head H1001 and copies it to the EEPROM in the printer body. The EEPROM in the printer body has at least two memory locations to store adjustment value for the O/E registration and the bi-directional registration. At first, the same content is stored in these two memory locations.
Upon reception of the printing apparatus or according to the frequency of use, the user may activate the registration processing (hereinafter called a user registration).
Using a printer driver PD, or a utility program, operating on a predetermined operating system OS of a host device HOST, which may be a personal computer, the user selects a registration mode with an input/display means CNSL including key, pointing device and display (step S2201). Then, the user sets a sheet of paper in the printer body M1000 and starts the printer (step S2202). The printer control unit PRC sends predetermined data to a drive unit HD of the head H1001, which then forms a pattern (
The numbers “+7” to “−3” on the left side of
As for other adjustment values “+7” to “+1” and “−1” to “−3”, the ejection timing of the odd-numbered nozzle columns is changed from the default value to +7 pixels and to −3 pixels in increments of one pixel, with the ejection timing of the even-numbered nozzle columns fixed. The + direction is for increasing the ejection timing time difference between the even-numbered nozzle column and the odd-numbered nozzle column. As already mentioned, as the face of the head between the even-numbered nozzle column and the odd-numbered nozzle column is bulged by ink swelling or temperature rise, the two columns tend to widen with elapse of time. Thus, the adjustment range in the plus direction is set large, up to 7 pixels (about 147 μm), and the minus direction is set up to −3 pixels (63 μm). The user can choose the most smooth pattern from among the range “+7” to “−3”.
All patterns for the O/E registration are printed by two-pass one-way printing (two forward or backward scans). The reason that the two-pass divided printing is used instead of one-pass printing is to ensure that the pattern smoothness is not impaired by factors other than the dot formation position deviations between the even- and odd-numbered columns, such as the individual nozzle variations. The reason that the one-way printing is performed is to ensure that the print is not affected by the dot formation position deviations between the forward and backward scans.
Applying this method to a random dithering method or an ordered dithering method using a matrix does not produce the effect described above. In the random dithering method, because the spatial frequency of the original pattern is distributed uniformly from low frequency to high frequency, deviations between the even-numbered rasters and the odd-numbered rasters do not result in a change in the spatial frequency distribution in the pattern. In the matrix-based ordered dithering, because the original image is completely cyclic, any deviation will cause a change in the spatial frequency of the pattern. However, because the entire pattern also changes similarly, regular alternations of dark and light parts rather than non-uniformity show. Such a pattern does not give a definite granular impression as in
Referring again to
In this embodiment, one raster of image is completed by four print scans. The first pass and third pass are printed by the forward scans while the second and fourth passes are printed by the backward scans. A 16-pixel forward printing area and a 16-pixel backward printing area are alternated as shown, with each area printed in two divided passes, first pass and third pass (or second pass and fourth pass).
When a bi-directional dot position deviation occurs, a black or white line appears at a boundary between the forward print area and the backward print area as shown in
The user then enters the adjustment value matching the selected pattern through the printer driver of the host device. The value thus entered is stored in the EEPROM 100 of the printer body.
The printer used in this embodiment outputs photographic images with high quality and allows the user to select between two carriage speeds according to usage: a mode in which the scan is performed at a carriage speed corresponding to the high image quality output (HQ mode) and a mode in which the scan is performed at a carriage speed about two times faster (HS mode).
This printing apparatus of this embodiment has a mechanism that enables adjustment in two steps of the distance from the platen to the carriage M4001 (referred to as a gap) to deal with such print media as thick sheets and envelopes. The gap can be set either to a standard position for normal printing or to a thick sheet position for printing thick sheets. The gap is adjusted by the user operating a gap adjust lever M2015 (
The gap adjust mechanism will be briefly explained. A sliding shaft of the carriage M4001 is mounted, under a force of an urging member such as spring, to a pair of gap adjust plates through a gap adjust lever 2015 at one end thereof and through a cam member at the other end. These gap adjust plates are adjustably fixed to the chassis of the printing apparatus so that the distance between the ejection surface of the print head cartridge H1000 and the print medium support surface of the platen can be set to an appropriate one.
Further, the gap adjust lever 2015 can be selectively set in two stop positions, an upper end position shown in
In the O/E registration and in the bi-directional registration, the appropriate adjustment value also changes according to the carriage speed and the gap. This embodiment has a mechanism that automatically carries out the registration according to this information.
In this embodiment, the actual printing is done according to the value shown in the table of
The above tables may not be determined only by calculations. For example. the adjustment value for a bi-directional printing that attempts to produce a uniform image with multiple passes may be slightly different from the adjustment value for a bi-directional printing that aims to produce a good ruled line with one pass. A possible explanation for this may be that in the multi-pass printing the nozzles in the nozzle column are selected in a scattered manner and driven, causing only a small temperature rise, while in the one-pass printing the number of nozzles driven simultaneously is large, causing a large temperature rise. An appropriate adjustment value needs to be set depending on what purpose the HS mode, HQ mode, standard position and thick sheet position are used for. Suppose, for example, an appropriate adjustment value used when ruled lines are printed in one pass is larger by “1” than the appropriate adjustment value used when a uniform halftone is printed in multiple passes. In this case, if only the one-pass monochromatic printing is performed in the HS mode, the registration for the HS mode should place an emphasis on the ruled line pattern. That is, a value larger by “1” may be written in advance into the table of
Further, the adjustment value for the bi-directional registration also changes slightly due to variations in the ejection speed of the print head. The ejection speed of the head used in this embodiment is 15 m/s at the center but actually it varies in a range of 12-18 m/s.
In other modes if their adjustment value differences from the normal mode do not change from those at the ejection speed of 15 m/s, the automatic adjustment can be done according to the automatic adjustment table of
In this case the problem can be solved by storing ejection speed information in the EEPROM 200 of the head H1001 and storing automatic correction tables corresponding to a plurality of speeds in the printer body. That is, in the above example the automatic correction table has two factors, carriage speed and gap position. One more factor, the ejection speed, is added. The automatic correction table in this case is shown in
A phenomenon is confirmed in which, depending on the initial state of individual heads, as the temperature of the head rises after a series of printing operations, the ejection speed also increases. Hence, when the head temperature increases during printing, the appropriate registration value also changes. Conversely, when the temperature returns to normal after printing, the appropriate registration value also returns to the original value. This change, however, cannot be dealt with by only the user registration. In that case, if a correlation between the head temperature and the ejection speed is taken, the registration can be executed in real time according to the initial ejection speed, present registration adjustment value and the head temperature at each moment.
Further, if the ejection speed table of
More concrete construction and processing to cope with these matters are described later.
While in this embodiment an example case of using the registration unit of one pixel has been described, other registration units may be adopted. Adjustments in units of half-pixel or smaller can be made distinguishable by using the adjustment patterns of
Mainly the automatic correction table for the bi-directional registration has been described. This invention is not limited to this embodiment. In the O/E registration, too, a change in the gap, carriage speed and ejection speed will result in a change in the appropriate adjustment value, so using the automatic correction table also for the O/E registration is advantageous.
It is difficult for the user to decide the proper timing for executing the registration after the printer has been received. It is desired that the correction be made before the image quality is degraded by repetitive printing operations. This embodiment allows the user to check the current adjustment state by using the head check pattern of the printer driver utility so that the user can recognize the need for the registration before the image deteriorates.
This check pattern can be output in a shorter time than all the patterns of
In the above embodiment, only yellow is excluded from the pattern because its check is not easy, and the actually output patterns cover five colors, Bk, C, M, LC and LM. Depending on the dye density of LC and LM, these ink colors may also be difficult to check. In that case, the user registration is performed only on Bk, C and M. For LC and LM, the same values as those of the colors which are on the same chip as LC and LM can be used. That is, at the step S2205 of
As described above, this embodiment is provided with a mechanism that enables the registration of even- and odd-numbered nozzles and the bi-directional registration to be initiated by the user as required and to be adjusted with high precision by using the high resolution print head formed with two nozzle columns for each color as shown in
Next, a second embodiment of the present invention will be described. This embodiment concerns a registration mechanism used when a bi-directional printing is performed by the interlace printing described in the Related Art.
As described by referring to
Hence, in this embodiment, the pattern of
When a bi-directional dot formation position deviation occurs, the patterns look similar to
A method of using normal dither patterns as bi-directional registration patterns, though not limited to the interlaced printing, has already been disclosed in Japanese Patent Application Laid-Open No. 11-48587 (1999). According to this method, as the specification reads, “a normal dither pattern, with dots regularly arranged in the main scan and sub-scan directions, can be perceived as being uniform without a gray scale variation when the print timing is appropriate. When the print timing is deviated, the dot intervals vary causing gray scale variations.” To be sure, the normal dither (an ordered dither using a matrix) has the original image arranged completely cyclically, so that any timing deviation will cause a change in the spatial frequency in the pattern. However, because the pattern as a whole also changes in the similar manner, this change is perceived as an overall density reduction or a regular repetition of dark and light parts, rather than nonuniformity. Further, because the cycle frequency of the dither pattern is significantly high, the change is often difficult to detect visually. The pattern of
With the provision of a mechanism that allows an inter-raster registration to be initiated by the user as required and to be adjusted highly precisely while performing the bi-directional interlaced printing, this embodiment makes it possible to maintain a high image quality at all times after the printing apparatus has been received.
While this embodiment feeds the paper a constant distance of nine pixels, this embodiment is not limited to this arrangement. As shown in
Next, a third embodiment will be described. Here, we will describe a case where a plurality of nozzle columns with a low resolution are arranged on a print head.
In this embodiment, too, image impairment due to ink landing position deviations among the nozzle columns is conceivable as in the first embodiment. It should be noted, however, that this embodiment requires not only an adjustment between even- and odd-numbered columns, but also adjustment for each of first column (nozzle column associated with the printing of first raster to (4n+1)th raster) to fourth column (nozzle column associated with the printing of fourth raster to (4n+4)th raster). This embodiment also uses a pattern similar to the first embodiment as the user registration pattern. Because the resolution is 2400 DPI, the image is obtained by giving 25% of data to the pixels corresponding to this resolution.
The pattern digitized by the conditional decision making method used in this invention is characterized in that even when there are many conditions (rasters) to be adjusted, a pattern with slight deviations and a pattern with no deviations at all can be clearly distinguished. This pattern, although it is a single pattern that contains a plurality of adjustment conditions, can exhibit its intended smoothness only when all the conditions are met. Hence, the pattern area to be printed is the same whether the number of conditions is two as in the above embodiment or four as in this embodiment.
This embodiment is provided with a mechanism that enables the registration of nozzle columns to be initiated by the user as required and to be adjusted with high precision by using the high resolution print head formed with four nozzle columns for each color as shown in
As described above, the 0/E registration depends on individuality of the print head and on the state of the print head including the environment and the print history. On the other hand, the bi-directional registration often depends on the characteristics of the printer body side, such as carriage encoder E0004 of the printer body and the distance between the carriage M4001 and the platen as a member for restricting a printing surface of the print medium. In the above first embodiment, therefore, the adjustment value for O/E registration is stored before shipment in a nonvolatile memory such as EEPROM installed at an appropriate location in the print head H1001 and the adjustment value for bi-directional registration is stored before shipment in a nonvolatile memory such as EEPROM installed at an appropriate location in the printer body.
The printer of the above construction can select one of two carriage speeds according to the mode in order to output a picture image with high quality. Further, to be able to print on thick sheets and envelopes, the printer has a mechanism for adjusting the carriage-to-platen gap in two positions. Hence, an appropriate adjustment value either in the O/E registration or in the bi-directional registration changes depending on the conditions, such as carriage speed, gap, and ink ejection speed and ejection angle from the print head H1001. So, the printer is provided with a mechanism that allows registration to be performed automatically according to these conditions.
In the bi-directional printing, in particular, the higher the resolution of the image, the more stringent the required dot landing position accuracy becomes. A dot landing position deviation of even several μm will result in a perceivable degradation of image quality. Hence, it is strongly desired to perform the bi-directional registration described above. It is also desirable to automatically correct the adjusted value for bi-directional registration according to the printing conditions.
The appropriate value of the bi-directional registration is influenced by the individualities or characteristic variations of the printer body, such as carriage speed and the platen-to-carriage gap, and also by the individualities or characteristic variations of the print head, such as ink ejection speed and ejection angle that change according to the mode of the printer.
The above embodiment employs a method that automatically changes the adjustment value for bi-directional registration when the user intentionally switches the printing state, as by changing the gap amount to allow the use of a thick sheet such as an envelope or by increasing the carriage speed in a mode that gives priority to the print speed.
As the printing resolution is increased further and the required dot landing position precision becomes correspondingly severe, the characteristic variations or tolerances of the printer body side such as carriage speed and gap or the characteristic variations or individualities of the print head such as ink ejection speed and ejection angle cannot be ignored. Further, the ink ejection speed and ejection angle also change over time and according to the state of the printing operation and thus it is strongly desired that the correction be made according to these changes.
In the following, we will explain about an embodiment that can determine an adjustment value for bi-directional registration precisely and in real time according to variation factors that can adversely affect the image quality, such as characteristic variations of printer body and print head as well as characteristic changes depending on the printing operation state or occurring with the passage of time.
The print head used in this embodiment to perform the bi-directional registration processing that takes the characteristic variations into account has the similar construction to that shown in
A main feature of this embodiment is an adjusting mechanism for bi-directional registration for the high-resolution printing. The bi-directional registration is affected not only by the factors dependent on the printer body characteristics, such as carriage speed and carriage-to-platen gap, but by the factors dependent on the print head characteristics, such as ink ejection speed and ejection angle. In this embodiment, because the resolution in the main scan direction is 2400 DPI, the bi-directional registration processing can be made at the 2400 DPI resolution for each pixel.
In the bi-directional printing, if ink is ejected when the carriage M4001 is at the same forward and backward positions, the inertia of the carriage scan speed causes the dot landing position on the paper during the forward (or backward) scan to deviate by several pixels from the dot landing position during the backward (or forward) scan. To cope with this problem, during the bi-directional printing in general, the ink ejection timings for the forward and backward scans are adjusted so that their dot landing positions on the paper will match. The adjustment value is shown on the ordinate in
If the carriage-to-platen gap tolerance of the printer body used in this embodiment is 1.4±0.2 mm and the normal print medium thickness is about 100 μm, then the distance from the nozzle to the print medium surface is 1.3±0.2 mm. The curves shown in the figure represent the relations between the adjustment value and the ejection speed for the three different carriage-to-platen gaps: minimum gap (1.2 mm), median gap (1.4 mm) and maximum gap (1.6 mm).
As can be seen from this diagram, even when a uniform ink ejection speed, 13 m/s for example, can be obtained, the adjustment value for registration deviates by ±2 pixels if the gap is within the tolerance range. Experiments conducted by the inventors have found that in the printer of this embodiment the deviation of about 20 μm (2 pixels) resulted in a perceivable degradation of the image quality. That is, if the gap is within the tolerance range, it is strongly recommended in practice that the registration processing be executed to form a high quality image.
In this embodiment the ink ejection speed from the print head is set at 13±3 m/s. In this case, too, even if a uniform gap of 1.4 mm, for example, is obtained, the adjustment value for registration will deviate by as much as ±2 to 3 pixels when the ejection speed is within the tolerance range. Considering this, it is strongly desired in practice that the registration processing be carried out to form a high quality image.
From the above description it is seen that the adjustment value for bi-directional registration can deviate greatly even at the initial stage depending on a combination of the printer body and the print head. For example, let us consider a case where a printer with the minimum gap tolerance is combined with a print head with the maximum ejection speed tolerance and a case where a printer with the maximum gap tolerance is combined with a print head with the minimum ejection speed tolerance. A difference in the adjustment value between these two combinations can be as large as 10 pixels.
In a configuration in which the print head is of a replaceable cartridge type and the user can make any desired combination between the print head and the printer body, as in the printer of this embodiment, one possible method is to have the user perform the user registration processing after the cartridge is mounted. The user registration processing, however, places a burden on the user and there is no assurance that the user, unfamiliar with the printer operation immediately after the printer has been delivered, can perform adjustments correctly.
It is therefore desirable that the registration be already completed by the time the printer body or print head delivered is first used.
For this reason, in this embodiment, factors affecting the bi-directional registration are classed into a group associated with printer body and a group associated with the print head, and the group of factors associated with the printer body, such as gap, is stored in a storage means on the printer body and the group of factors associated with the print head, such as ejection speed, is stored in a storage means on the print head. These groups of factors become valid only when both of them are stored. This is explained in the following. Let us consider a case where the ejection speed is stored only in the storage means on the print head with nothing stored in the storage means on the printer body. In that case, if the median value of the ejection speed of 13 m/s is obtained, for example, the gap tolerance alone can produce a deviation of 6 pixels (
In this embodiment, the printer body and the print head each have a nonvolatile memory such as EEPROM as their storage means, in which the information on gap and ejection speed is stored in advance so that the registration processing can be done as soon as the print head is mounted on the printer body after the print head or printer body has been delivered. For this embodiment, the construction similar to the one shown in
That is, when the tolerance of the ejection speed of the print head is 13±3 m/s, the tolerance is divided at intervals of 1 m/s into seven sections coded “01” to “07” for example, one of which is then stored in the EEPROMs 200 of the print head as the unique characteristic value of the print head. When the gap tolerance is 1.4±0.2 mm, this tolerance is divided into three sections coded “01” to “03” for example, one of which is then stored in the EEPROM 100 of the printer body as the unique characteristic value of the printer body.
When, for example, a print head with an ejection speed of 11 m/s and a printer body with a gap of 1.4 mm are combined, the EEPROM of the print head is stored with a code “02” and the EEPROM of the printer body with a code “02”. When the power is turned on, the adjustment value table for registration (
As described above, with this embodiment, by simply storing the ink drop ejection speed in the EEPROM of the print head and the carriage-to-platen gap value in the EEPROM of the printer body, a high quality image adjusted by the bi-directional registration can be obtained without troubling the user immediately after the printer is delivered to the user.
Next, another embodiment will be explained which automatically performs bi-directional registration processing in response to a temperature rise during printing.
As explained in
Also to guarantee a proper registration even when there is a temperature rise, this embodiment adopts a configuration in which the printer body has a table by which to refer a registration adjustment value table according to the print head temperature.
Consider a case, for example, where the user mounts a print head having an initial ejection speed of 12 m/s on a printer body whose carriage-to-platen gap is 1.4 mm. Before a printing for the first page is started, the CPU (printer control unit PRC) on the printer body checks the temperature of the print head. If the print head temperature falls in a range of 20-30° C., the ejection speed of “03” (12 m/s) is obtained from the table of
Suppose, after repeating this printing for several pages, a head temperature of 30-40° C. is detected. In that case, an ejection speed “04” (13 m/s) is determined from the table of
As described above, before starting to print each page, the print head temperature is checked and the adjustment value for registration is automatically adjusted for each page to minimize degradation of image quality due to temperature change while printing.
Although the above-mentioned automatic adjustment for registration that is carried out upon delivery of a printer has been described to be corrected for each page, this correction may be made otherwise.
The registration processing initiated by the user's judgment (user registration), which was described referring to
The user registration in this embodiment has the similar configuration to
The user selects a registration mode in the utility of the printer driver PD on the host device HOST by using the input/display means CNSL (step S2201). The user then sets paper on the printer body and starts the print (step S2202). In response to this step, the printer control unit PRC sends predetermined data to the drive unit HD of the print head H1001 which forms a pattern for registration (
A column F of
The patterns corresponding to “+5” to “−5” are printed by fixing the ejection timing during the forward scan and changing the ejection timing during the backward scan in increments of one pixel, as in the case of
The bi-directional registration patterns and the printing method are also similar to those explained in
In this embodiment, too, each raster of an image is completed by four printing scans, with the first and third pass printed in the forward scan and the second and fourth pass printed in the backward scan. As shown in
When a bi-directional dot position deviation occurs, a black or white line appears at a boundary between the forward print area and the backward print area as shown in
The user registration described above can be performed whenever the user thinks it necessary. It may however not be possible to cope with constantly occurring changes, such as dot landing position variations caused by the rising temperature as a result of continuous printing. Even under such a circumstance, a satisfactory image is obtained by using the table of
With this embodiment described above, the ink ejection speed that changes according to the print head temperature is estimated and, based on this estimated value, an appropriate correction is made at any time to the normal-temperature adjustment value for registration currently being used to print.
It is assumed that the printer applying this embodiment has three carriage speeds that can be selected according to use and situation: a HQ1 carriage speed mode for normal high image quality, a HQ2 carriage speed mode slightly slower than HQ1 and selected according to a rise in the print head temperature, and an HS carriage speed mode for fast scan. Normally, the printing is done at the HQ1 carriage speed. When the print head temperature rises to a level that will pose a problem to the image, as during continuous printing, the HQ2 carriage speed is used. When the print head temperature rises above the normal temperature, the ink drop ejection state becomes unstable, so that the drive frequency is lowered to an appropriate level to stabilize the image quality. The print head used in this embodiment performs the ejection operation at the drive frequency of 25 KHz during the normal printing (HQ1 carriage speed), at the carriage speed of 20.8 inches/sec. The print head temperature is checked for each page and when it is higher than 45° C., the drive frequency is set to 20 KHz from the next page. At this time, the carriage speed is set to 16.7 inches/s.
The HS mode is specified by the user when he or she wants a quick printout. The carriage speed in this mode is 29.2 inches/s.
To deal with such print media as thick sheets and envelopes, the printer of this embodiment has a mechanism that can adjust the carriage-to-platen gap in two positions: a standard position for normal printing and a thick sheet position for printing thick sheets. The gap is adjusted by the user operating the gap adjust lever M2015. There is the gap sensor E0008 to check whether the present gap is in the thick sheet position or the standard position, and thus the printer body can perform the print control that matches the present gap.
In the case of a print head with an initial ejection speed of 13 m/s, for example, the EEPROM 200 of the print head H1001 is stored with a code “04”. When the initial print head temperature is about 25° C., the ejection speed of 13 m/s is obtained from the table of
The print head temperature gradually rises as the printing continues. Suppose the print head temperature is 35° C. before starting the third page printing. At this time, from the table of
Suppose the print head temperature of 47° C. is detected when a fifth page is to be printed. In the same way as described above, the table of
In this embodiment, at the head of each page the print head temperature is checked and the ejection speed at that time is determined from the matrix of the initial ejection speed and the print head temperature. Further, from the detected print head temperature, a drive frequency for that page is determined and then a final adjustment value for registration is obtained from the determined drive frequency and the calculated ejection speed.
This makes it possible to produce the similar effect to that of the above-described embodiment, i.e., to be able to cope in real time with the registration deviations caused by temperature changes which are difficult to adjust with the initial setting or the user registration. In addition, the above-described method also makes it possible to form a stable image without burdening the print head even when the temperature rises as a result of continuous printing.
In this embodiment, although for the sake of simplicity no explanation has been given as to the adjustment using the table of gap tolerance that was considered in the preceding embodiment, this adjustment can of course be performed. The effect similar to that described above can be obtained if the gap is classed into three categories, large, medium and small gaps, for each drive frequency.
As explained in this section where three embodiments have been described, a memory means for storing dot position information associated with the characteristic variation or individuality of the printer body is installed in the printer body and a memory means for storing dot position information associated with the characteristic variation or individuality of the print head is installed in the print head; and when the print head is mounted on the printer body to print an image, the contents of both memory means are referred to to determine the information for use in the dot position adjustment. This makes it possible to properly correct characteristic variations due to tolerances of carriage-to-platen gap and ejection speed.
Further, during the bi-directional registration, the ink ejection speed is estimated according to the detected print head temperature and, based on the estimated ejection speed, the information used for adjusting print position on the print medium is determined. This processing enables an appropriate adjustment value to be determined in real time in response to a change resulting from the state of the printing operation.
One form of the head to which the present invention can be effectively applied is the one that utilizes thermal energy produced by an electrothermal transducer to cause film boiling in liquid thereby generating bubbles.
In the embodiment described above, the printer driver PD on the host computer HOST side supplies image data to the printing apparatus. The data of registration pattern as shown in
The scope of the present invention also includes a print system in which program codes of software or printer driver that realize the function of the above embodiment are supplied to the computer in a machine or system to which various devices including the printing apparatus are connected, and in which the program code stored in the computer in the machine or system are executed to operate a variety of devices, thereby realizing the function of the above-described embodiment.
In this case, the program codes themselves realize a novel function of the present invention and therefore the program codes themselves and means to supply the program code to the computer, such as storage media, are also included in the scope of this invention.
The storage media to supply the program codes include, for example, floppy disks, hard disks, optical disks, CD-ROMs, CD-Rs, magnetic tapes, nonvolatile memory cards and ROMs.
The scope of this invention includes not only a case where the function of the above-described embodiment is realized by executing the program codes read by the computer but also a case where an operating system running on the computer performs, according to directions of the program codes, a part or all of the actual processing and thereby realizes the function of this embodiment.
Further, the scope of this invention includes a case where the program codes read from a storage medium are written into a memory in a function expansion board inserted in the computer or into a memory in a function expansion unit connected to the computer, after which, based on directions of the program codes, a CPU in the function expansion board or function expansion unit executes a part or all of the actual processing and thereby realizes the function of this embodiment.
As described above, according to the present invention, a mechanism is provided that enables the inter-raster registration to be initiated by the user as required and to be adjusted highly precisely by using the high resolution print head formed with a plurality of nozzle columns arranged side by side in the main scan direction or by performing a bi-directional interlaced printing method. This mechanism makes it possible to maintain high image quality at all times after the printing apparatus has been received.
Further, it is also possible to set the dot position adjustment value properly and in real time according to characteristic variations, within tolerance, of the print head and the printer body as well as according to the state of the printing operation.
The present invention has been described in detail with respect to preferred embodiments, and it will now be apparent from the foregoing to those skilled in the art that changes and modifications may be made without departing from the invention in its broader aspects, and it is the intention, therefore, that the appended claims cover all such changes and modifications as fall within the true spirit of the invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 11-236260 | Aug 1999 | JP | national |
| 2000-219758 | Jul 2000 | JP | national |
This application is a division of application Ser. No. 09/639,743 filed Aug. 15, 2000 now U.S. Pat. No. 6,960,036.
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| Number | Date | Country | |
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| Number | Date | Country | |
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| Parent | 09639743 | Aug 2000 | US |
| Child | 11207817 | US |
